The present invention relates to a method and system for controlling the operation of an automotive engine, and more particularly to a learning control system for updating data stored in a table for the learning control.
In a learning control system, updating of data is performed with new data obtained during the steady state of engine operation. Accordingly, means for determining whether the engine operation is in the steady state is necessary. A conventional learning control system (for example Japanese Patent Application Laid Open No. 56-165744 corresponding to U.S. Pat. No. 4,309,971) has a matrix (two-dimensional lattice) comprising a plurality of divisions, each representing engine operating variables such as engine speed and engine load. When the variables continue for a predetermined period of time in one of the divisions, it is determined that the engine is in the steady state. On the other hand, a three-dimensional look-up table is provided in which a matrix coincides with the matrix for determining the steady state. Data in the look-up table is updated with new data obtained during steady state.
In such a system, if the engine operating variables fluctuate in two adjascent two divisions over the border line between both divisions without staying in one of the divisions during the predetermined period of time, the system can not determine such a state as a steady state, although such a state should be determined as a steady state. Accordingly, data corresponding to both adjacent divisions are not updated, which delays the correction of data and reduces the frequency of the learning. This means that the motor vehicle is driven by fuel having an improper air-fuel ratio, which increase fuel consumption and reduces driveability.